The present invention relates to a gas-sterilizable package which has a lower foil of thermoplastic material and formed as a shell, and an upper foil of paper or thin fleece and connected with the lower foil along the edges of the foils by welding or sealing. The invention also relates to a cover for the package, as well as to a method of producing the package.
Packages of the above mentioned general type are known in the art and widely used. They are utilized in particular for packing of tools or objects which are required during operations, and must be kept in sterile condition. The upper foil is composed of paper and thereby of fibers. Sacks are also known which use fibers of synthetic plastic materials, so as to guarantee required gas permeability for sterilization by gas, particularly hot steam. In the known packages the release of welding connections between upper foil and lower foil requires a certain force application, since in many cases the fibers are torn from the upper foil and they remain adhesively connected mainly to the welding connection of the lower foil. In many cases the torn out fibers reach the packed objects. A further danger is that the packed metallic devices, such as the above mentioned tools for an operation, rub during transportation of the packages against the inner surface of the paper or fleece layer and thereby also release the fibers which deposit in many cases on the tools. For eliminating the above mentioned disadvantages it was proposed to apply a wax coating on the paper or fleece layer at their side facing toward the interior of the package. This wax coating has the advantage that it forms a peelable welding connection of the paper or fleece layer with the lower foil and reduces the wear by the metal devices in the sack. However, it also possesses the disadvantage that the wax coating of the foil of paper or fleece considerably affects the gas permeability during gas treatment for the purpose of sterilization or vacuum deep drawing in autoclaves. The considerably reduced permeability can be compensated only by a longer time of the application of the gas treatment which increases the costs of the process. When the gas treatment or the vacuum drawing is performed in a fast cycle, it leads to swelling up and tearing of the sack or similar package.